1. Remove battery compartment cover, then put a AAA battery in and replace the battery cover. After that, open the probe, all segments of the LCD will be activated2. ON/OFF button: Press "On/off" key for power on/off3. Toggle Switch: Shift the toggle switch under the battery compartment cover to choose unit display in " Fahrenheit " or “ Celsius ”4. Test temperature by inserted probe into thickest part of food5. "Hold:" button : Before remove the probe from food, press " hold " button to hold temperature reading until be pressed again6. Unit will automatically turn off after 10 minutes if no any buttons be pressed